.collapsibleList li {
  list-style-image: url("button.png");
  cursor: auto;
}

li.collapsibleListOpen {
  list-style-image: url("button-open.png");
  cursor: pointer;
}

li.collapsibleListClosed {
  list-style-image: url("button-closed.png");
  cursor: pointer;
}

#seitenhintergrund {
  background-color: blue;
}